1. Field of the Invention
The present invention relates to a technique of executing efficiently bookbinding operation with a bookbinding apparatus in a printing system that has a printing apparatus to which the bookbinding apparatus is connected, and a controller that supplies printing data to the printing apparatus and causes it to execute printing.
2. Description of the Background Art
In recent years, there has come in practice a digital printing apparatus that can directly print on a sheet printing data created by a desktop publishing application running on a computer in general use, without passing through a plate making step. There is also being developed such a printing system that performs consistently from page data creation to bookbinding by directly connecting a bookbinding apparatus to such a digital printing apparatus and sending a printed sheet delivered from the digital printing apparatus into the bookbinding apparatus.
On the other hand, in general printing, a plurality of printing images represented by printing data are imposed on one side of a sheet in consideration of stitching. Also in the digital printing apparatus, it is preferable to execute such imposition prior to printing.
There is however the problem that when a bookbinding apparatus is connected to a digital printing apparatus, the printing apparatus is required to execute imposition in consideration of a sequence in which the bookbinding apparatus picks up sheets.
It is now proposed to consider a particular case of printing a document consisting of eight pages on two sheets Pa and Pb, for example, assuming that a direction of folding is “left-hand opening” and the setting of stitching is “saddle stitching.” In this case, page 8 and page 1 are imposed on the top side of sheet Pa, page 2 and page 7 are imposed on the back side of sheet Pa, page 6 and page 3 are imposed on the top side of sheet Pb, and page 4 and page 5 are imposed on the back side of sheet Pb. The digital printing apparatus delivers sheets Pa and Pb on which the printing images represented by their respective printing data are imposed. At this time, the printing apparatus stacks the sheets such that an earlier printed sheet is located at a lower position. Therefore, if the bookbinding apparatus picks up sheets from the lowermost position of the stacked sheets, the bookbinding apparatus picks up sheet Pa and Pb in the order named, thereby obtaining the document arranged in the correct sequence.
However, if the bookbinding apparatus picks up sheets from the uppermost position of the stacked sheets, the bookbinding apparatus picks up sheet Pb and Pa in the order named, thereby failing to obtain the document arranged in the sequence. Therefore, if the bookbinding apparatus picks up sheets from the uppermost position of the stacked sheets, an operator of the digital printing apparatus is required to impose page 6 and page 3 on the top side of sheet Pa, page 4 and page 5 on the back side of sheet Pa, page 8 and page 1 on the top side of sheet Pb, and page 2 and page 7 on the back side of sheet Pb.
This causes the problem that an operator of the digital printing apparatus cannot perform imposition unless the operator is well acquainted with the sequence in which the bookbinding apparatus connected to the digital printing apparatus picks up sheets.